1. Field of the Invention
The present invention relates to a novel, economical, industrial process for producing p-n-alkylbenzoic acids which are important intermediates for liquid crystals.
2. Description of the Prior Arts
It is quite important to obtain a p-n-alkylbenzoic acid, nevertheless it has been quite difficult to attain an economical industrial process for producing p-n-alkylbenzoic acid because branched alkylbenzoic acids or o- or m-alkylbenzoic acids or other by-products are produced.
Heretofore, the conventional processes for producing p-n-alkylbenzoic acids are as follows.
(1) Benzene is acylated with n-aliphatic acid chloride by Friedel-Craft reaction to obtain n-alkylphenyl ketone and then, carbonyl group of the ketone is reduced to obtain n-alkylbenzene and then, n-alkylbenzene is converted into p-n-alkylacetophenone by reacting acetyl chloride and acetyl group of the resulting p-n-alkylacetophenone is oxidized by an oxidizing agent such as hypobromite to obtain p-n-alkylbenzoic acid as disclosed in U.S. Pat. No. 3,683,040, U.S. Pat. No. 3,697,594, U.S. Pat. No. 3,764,621 and U.S. Pat. No. 2,383,874;
(2) p-n-Alkylaniline is converted into p-n-alkylbenzonitrile by diazotizing it and reacting with an aqueous solution of cuprous cyanide and then p-n-alkylbenzonitrile is hydrolyzed into p-n-alkylbenzoic acid as disclosed in Japanese Unexamined Patent Publication No. 73384/1973;
(3) n-Alkylbenzene is converted into p-n-alkylbenzoic acid with oxalic dichloride by Friedel-Craft reaction as a special method.
In accordance with these conventional processes, the reaction steps are complicated and much and cause many side-reactions and a separation of isomers is not easy and moreover, large amounts of expensive reagents such as aluminum chloride are required and a treatment of waste drainages is not easy, and the resulting p-n-alkylbenzoic acid is expensive.